The ting is that if you install PyCharm from the software Center, its not the community edition and you have to login with an JetBrains account if you want it to work. the community edition do not require this.

Linux Installation Instructions
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1. Unpack the PyCharm distribution archive that you downloaded to
where you wish to install the program. We will refer to this destination
location as your {installation home} below.

2. Open a console and cd into "{installation home}/bin" and type:

./pycharm.sh

to start the application. As a side effect, this will initialize various
configuration files in the ~/.PyCharmCE2017.3 directory.

3. [OPTIONAL] Add "{installation home}/bin" to your PATH environment
variable so that you may start PyCharm from any directory.

4. [OPTIONAL] To adjust the value of the JVM heap size, create
~/.PyCharmCE2017.3/pycharm.vmoptions (or pycharm64.vmoptions
if using a 64-bit JDK), and set the -Xms and -Xmx parameters. To see how
to do this, you can reference the vmoptions file under
"{installation home}/bin" as a model.

[OPTIONAL] Changing the location of "config" and "system" directories
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By default, PyCharm stores all your settings under the ~/.PyCharmCE2017.3/config
directory and uses ~/.PyCharmCE2017.3/system as a data cache.
If you want to change these settings,

1. Open a console and cd into ~/.PyCharmCE2017.3/config

2. Create the file "idea.properties" and open it in an editor. Set the
idea.system.path and/or idea.config.path variables as desired, for
example:

idea.system.path=~/custom/system
idea.config.path=~/custom/config

3. Note that we recommend to store data cache ("system" directory) on a disk
with at least 1GB of free space.